DESCRIPTION (APPLICANT'S ABSTRACT): Insomnia is a sleep disorder characterized by a chronic difficulty in initiating and maintaining sleep which has a relatively high prevalence and a significant socioeconomic cost. There is good evidence that cognitive and/or physiological arousal, associated with sustained sympathetic activation, is one of the underlying causes of insomnia. Relaxation treatments such as progressive relaxation and meditation which address the cognitive and somatic arousal associated with insomnia have been found to be effective. Yoga is a comprehensive discipline which includes physical exercises, postures, breathing techniques, and meditation, for the purpose of improving health and well being. Research studies have documented the effectiveness of yoga in reducing sympathetic activation and cognitive and somatic arousal and in the treatment of specific medical disorders. Although it has been used and recommended for the treatment of insomnia, its effectiveness has not been evaluated in a randomized, controlled study. The aim of this proposal is to evaluate the effectiveness of daily yoga practice in the treatment of chronic psychophysiological insomnia in a randomized, controlled study. A subjective measure of sleep onset latency will be derived from daily sleep diaries, and an objective measure will be drawn from polysomnographic recordings. Sleep onset latency will be evaluated before and after a two month treatment period in a total of 48 young men and women who have been carefully screened for the presence of psychiatric and medical disorders which might contribute to a primary complaint of insomnia. Subjects will be randomized equally into a yoga treatment group and an untreated control group. We anticipate that yoga practice will prove to be an effective treatment for insomnia which will yield significant improvements in sleep onset latency relative to untreated control subjects. We also anticipate that these improvements will be maintained at long-term follow up evaluation.